July 15, 2019
Simply put, a point load is a non-uniform load – think the wheels of a cart, or a nail tip sticking out of the bottom of a pallet. All floors have a compressive strength (load per area in pounds per square inch) that the floor can withstand before failing. A surface area significantly smaller than one square inch will take significantly less load to exceed the strength tolerance, making floor protection in this situation vital.
The physical damage and scratches caused by high point loads will appear lighter in color than the surrounding areas. This difference in appearance is mostly due to physics of light scattering over the micro-roughness of the surface within the scratch. Deeper gouges will also appear lighter for this reason, in addition, the gouge will be accentuated due to the aggregate being crushed by the point load. These gouges can also amber over time as the UV stable top coat is damaged, exposing the body coat of the floor.
Let’s look at 3 common causes of point load damage and what you can do to keep this from happening to your resinous floors.
1. Vertical drops of sharp or thin objects Significantly smaller areas can only withstand smaller loads. For example, a one inch square of floor can withstand a compressive load of 17,500 lbs; while a 1/16” by 1/16” square area (1/256 of a square inch) area can only withstand a compressive load of less than 68 lbs.
When is this likely to happen? Dishwashing areas where utensils, pots, and pans are regularly dropped, or areas where metal tools and knives are regularly handled.
How to prevent it? Place a protective rubber mat in front of dish sinks or at workstations where drops are most likely to happen.
2. Wheels that are too small or damaged Consider a four-wheel cart on small hard wheels, each wheel having about 1/32nd of a square inch contact with the floor surface. For a floor with a 17,500 per square inch compressive load rating of 17,500 psi divided between 4 wheels at 1/32 square inch equals a point load of approximately 137 lbs per wheel. However, if a hard object is embedded in one of the wheels the point load is greatly magnified in the area of obstruction.
When is this likely to happen? Wheels that are too small for the weight of the cart or have embedded debris in them, think hospital gurneys, supply carts, delivery carts going from outdoors to inside.
How to prevent it? Use large rubber wheels on carts vs. small plastic or metal wheels. When going from areas of high debris such as outdoors roll over a sticky mat or carpet to remove debris. If excessively heavy (example: fully stocked wheeled storage shelving) store on a mat or sheet of plywood to help spread out the point load.
3. Point load applied at an angle Non-compressive point loads applied at an angle with respect to the surface take significantly less force to result in physical damage. The adhesion, tensile and flexural properties of the floor system are lower than its compressive strength. In addition, the force applied is often amplified by mechanical advantage via a combination of the object shape and the angle at which force is applied.
When is this likely to happen? Most commonly seen in manufacturing and warehouse areas, for example, when a pallet with a nail tip sticking out is dragged across the floor surface or the claw of a hammer impacts the floor.
How to prevent it? When moving pallets lift them slightly off the ground using a pallet jack or forklift or use temporary floor protection such as a layer of plastic sheeting.
There you have it, the three most common causes of point load damage and what to do to prevent them. To sum it all up nice and sweet:
To protect the floor from scratches when moving equipment, the use of temporary floor protection such as Ram board (or equivalent) is recommended. If using Masonite or plywood, apply a layer of plastic sheeting such as Visqueen (or equivalent) underneath the wood.
For specific compressive, tensile or flexural strength of your flooring system of choice speak to your Technical Services Manager. We’re also available to help you determine the best system for you based on how you use your space on a daily basis.
Author: Rob Pacheco Jr.
Rob is responsible for Applicator Development and Tech Services in the Northeast / Mid-Atlantic regions for Dur-A-Flex. His role includes jobsite support, answering technical/application questions and applicator development.